dy/dx command

The dy/dx command finds a numeric derivative, which approximates the first
derivative of an expression with respect to the x variable at the trace cursor
location while viewing a graph.

While viewing the graph of a function, press
to view the Derivatives functions.

Press .

If more than one function is graphed, use
to select the desired curve. Enter the x-coordinate of the point on the curve
for which the value of the derivative is needed (or trace the curve to the
approximate point) and press .
The value (or approximate value) of dy/dx at the point is displayed at the
bottom of the screen.

Note: The number of decimal places shown can be changed in the MODE menu.